Automobiles are equipped with seat belts and airbags to provide safety for passengers. In recent years, there is a trend for controlling the operation of such safety devices according to the body weight of a passenger. For example, the amount of gas to be introduced into the airbag, an airbag inflating speed, or a pre-tension of the seat belt may be adjusted according to the weight of a passenger. To optimally use these safety devices, the weight of the seat's occupant must be measured.
Several devices have been designed to measure the weight of the occupant while seated. Most of these devices use some form of sensor to measure forces transmitted to it. Many of these devices, however, do not provide an accurate measure of the occupant's weight because additional forces other than the occupant's weight are also measured by the sensor. Specifically, the seat and any sensor coupled to the seat is subject to error-inducing loads caused by forces in the X, Y, and Z directions and moments about the X, Y, and Z directions. Examples of these error-inducing loads include horizontal forces caused by assembly forces or an occupant in the rear of the vehicle pushing on the seatback, twisting moments caused by a leaning occupant, non-vertical load components caused by the occupants weight during acceleration and deceleration of the vehicle, and the like. These error-inducing loads (or forces) can be transferred to the sensor and cause the sensor to generate incorrect information.